A conventional type of the winding apparatus winds the wire the sectional shape of which is circular on a bobbin 21 as shown in FIG. 15. Since the coil is required to have a high density of wires in order to decrease the volume of the equipment which uses the coil, the wire 20 is wound to be aligned. The coil shown in FIG. 15, however, cannot make the density of wire maximum even though the wire 20 is aligned in the correct order. Since the sectional shape of the wire 20 is circular, at least a certain amount of space remains between the wires adjacent to each other.
In order to reduce the void between the adjacent wires, a wire the sectional shape of which is square (square wire) may be used instead of a circular wire. According to the present inventors' study, a coil wound with square wire has the following disadvantages. Since the square wire should be uncoiled from a drum in order to be supplied to the bobbin, and since twisting of the square wire should be carefully avoided, the drum must be rotated when the square wire is uncoiled from the drum in order to avoid twisting of the square wire. Hence, such uncoiling apparatus is complex and requires much capital cost. The position of the square wire should be carefully controlled in order to align the square wire on the bobbin. Therefore, the orientation of the square wire from the uncoiler to the bobbin must be carefully controlled. Furthermore, since the end portion of the wire must be connected to the bobbin by the end of the wire being wound around the terminal of the bobbin, it is difficult to avoid twisting the wire after the end portion of the wire is wound on the terminal of the bobbin. Consequently, it is difficult to align the square wire on the bobbin. As described above, the square wire can be adapted only on the special shape of the coil.